Means for damping the rolling motion of ships.



H. FRAHM.

MEANS FOR DAMPING THE ROLLING MOTION OF SHIPS.

APPLIOATIOH FILED Mn 4, 1909.

970,368. Patented Sept. 13,1910.

PATEN T OFFICE.

HERMANN FRAHM, OF HAMBURG, GERMANY.

MEANS FOR DAMPING THE ROLLING MOTION OF SHIPS.

Specification of Letters Patent.

Patented Sept. 13, 1910.

Application filed May 4, 1909. Serial No. 493,909.

To all whom it may concern:

' Be it known that I, HERMANN FRAHM, a citizen of the free town of Hamburg, and resident of 18 Kloster Allee, of .the free town of Hamburg, in the German Empire, engineer, have invented new and Improved -Means for Damping the Rolling Motion of dampin one side of the ship Ships, of which the following is a specification.

This inv ntion relates to means used for the rolling of ships by means of the osci lation of quantities of water from to the other through a holder, as describe in the application filed by me on the 15th day of July, 1908, bearing Ser. No. 443,597.

- t has hitherto been proposed to provide a plain holder arranged crosswise in the ship and having the upper water surface free. This arrangement however possesses many disadvantages which render it impracticable. In order to obtain a damping action by the oscillating motion of water in a holder it is necessary that the period of the oscillations of the water correspond approximately to the natural oscillations of the ship. It is further necessary that there should be a base difl'erence between the oscillations of the water and those of the ship. Such results cannot be obtained in a vessel in which the water has a free upper surface from side to side of the ship and further the hammering action of the water on the sides and ends of the container soon damages the container.

The objections of former constructions are avoided in the present invention by employing a holder which is of substantially U- form with the two legs of the U arranged vertically and the lower bridging part constantly filled with water. In this way the water in its oscillations is caused to follow a fixed path and all hammering action is avoided.

The entire water holder according to the present invention consists substantially of two side vessels connected at their lower ends with a cross pipe through which the water is guided as it oscillates from one side of the shi to the other during rolling of the ship. If the cross connection and the side vessels have the same cross section the period of oscillation of the water corre sponds to the length of the column, but this period is altered if the cross sections of the side vessels and the cross connection are different, that is to say if the cross connection is made of smaller cross section than the side vessel parts, the riod of oscil- \lation is increased. It is o greater importance however to rovide means for ad usting the period 01 oscillation of the water and this result may be obtained in several ways, for instance the side vessels may be arranged widening toward their upper ends and the control of the periods effected by altering the amount of water in the entire holder. The adjustmentmay also be effected by introducing a throttling organ in the cross connection or the throttling may be obtained by throttling the exit of air from the upper ends of the side vessels.

The invention is illustrated diagrammatically in the accompanyingdrawing.

Fi ure 1 is a cross section through a ship provided with an apparatus for damping the rolling mot-ion of ships which; embodies in desirable form the present invention. Figs. 2, 3, and 4 are modifications. of the device illustrated in Fig. 1.

In carrying the invention into effect according to the form shown in Fig. 1 the side vesselsa and b are connected at their lower ends by means of a cross connection (I. The cross connection (Z is of smaller cross section than the average cross section of the vessels a and b, so that a certain amount of throttling is introduced by this difference in cross section. In order to increase this throttling to meet different requirements in the ship I may introduce a throttling organ e into the cross connection as shown in Fig. 2. In a device of this kind the flow of the water from the vessel a to the vessel 1) and vice versa is retarded by the throttling action obtained by the cross connection alone or the cross connection with the throttling device e. The damping action is obtained in that the force of the swinging motion of the ship transmitted to it at each oscillation by the waves is destroyed by the throttling. When the waves are in synchronism with the natural oscillations of the ship, the ship onlyoscillates as far as this throttling action permits. The actual amount of the oscillation is that at which the force transmitted at each wave impulse to the ship is exactly equal to the energy lost by throttling in the manner mentioned above. The damping action is of course increased with increased quantities of water in the holders. The amount of the throttling action is of ject into the holders so that when the water rises in the said holders the exit of air from the upperend of the holders is throttled. In Fig. 3ithere is also shown a valve 0 in the connection d so that throttling may be also effected by adjusting the valve 0 As shown on the pipe 9 the end of this pipe may be-beveled so as to obtain a gradual throttling action. The throttling action may also be secured in the manner shown in Fig. 4:. In this figure the pipes p and q are provided with valves 10 and g by which the exit of air. from the holders a and b may be throttled. The throttling of air may also be efiected in the manner shown in Fig. 2 in which the upper end of the vessels a b are connected by a pipe having a valve therein. In this way the oscillation of the air from the vessel a to b is also throttled and the required adjustment thereby etconduit of uniform cross section the period t of the oscillation is given by the formula (I) war in which 11,; is equal to half the effective length of the water column. If the water column is composed of parts of different cross section, say for simplicity two cross sections F and f, then if the part of section F has the length and the part of section 7 has the length 'l O The period of oscillation of the water column can therefore be altered by altering any of the quantities in equationII above. The

present invention provides means by which the quantity L may be very simply and at the same time eifectively altered.

The method of altering the period by a1- tering L is illustrated diagrammatically in Fig. 1.- The characteristic feature of this arrangement consists in arranging the liquid holder in the form of a U with widened or funnel shaped ends. With a holder of this kind it is not necessary to alter the holder or connecting pipe in any way but nevertheless the magnitude ofthe quantity L in the equationsgiven above may be altered within sufliciently wide limits to meet the requirements of practice merely by filling the water container more or less as required. In Fig.

1 the quantitiesL Z F f are indicated. The widenedparts a and b are arranged at the sides of the ship and the connecting part d is of constant cross section from the plane mm on one side to the plane mw on the other side. From these planes the ends a and b gradually increase in cross section. It is also possible to arrange the cross connecting piece with an enlarged center piece or of any other non-uniform cross-section. For the approximate calculation of the period of oscillation of such a column however it is advisable to take the length Z as extending to the line 02'-:v'. The distance fromww to the water level F represents the quantity L. If now the water is filled until the average section of the water in the holders a and 1) reaches the point F then In this way the period of'oscillation of the water column can be very simply altered to meet the conditions of loading or any other conditions to which the ship may be subjected during the voyage. Even comparatively small, alterations in the level'of the water in the holders a and I) produce Very considerable results on the length Lm.

It will be understood that the arrangements described may be combined in many ways and slightly modified as desired.

I claim j 1. In ships, means for damping the roll-' ing movements caused by the impacts of the waves,comprising a water Vessel at each side of the ship, a cross connection joining the. bottoms of said vessels to form a substantially U-shaped passage in a vertical plane, and means for maintaining the air above the water levels in both vessels under the same pressure, said U-shaped passage being so dimensioned and filled with water which is free to oscillate, that the period of said oscillations of the water from side to side of the ship, on the occurrence of rolling movements-are substantially equal to the natural period of oscillation of the ship.

2. In ships, means for damping therolling movements comprising a water vessel at each side of the ship, a cross connection for moses the bottoms of said vessels to form a substantially U-shaped passage in a vertical line and means for throttling said cross connection, said U-shaped passage being so dimensioned and filled with water that the period of oscillation of the water from side to side of the ship, on the occurrence of rolling movements will be substantially equal to the natural period of oscillation of the ship. a

3. In ships, means for damping the rolling movements comprising a closed water vessel at each side of the ship, a pipe leading 'from the upper end of each of said vessels, means for throttling said pi e, a cross connection joining the bottoms 0 said vessels to form a substantially U-shaped passage in a vertical plane, said U-shaped passage being so dimensioned and filled with water that the period of oscillation of the water from side to side of the ship, on the occurrence of rolling movements, will be substantially equal to the natural period of oscillation of the ship. I

4. In ships, means for damping the rollin movements comprising a closed water vesse at each side of the ship, a pipe leading from the upper end of. each of said vessels, means for throttling said pipe, a cross connection for the bottoms of said vessels'to form a substantially U-shaped passage in a vertical 'plane, and means for thrittling said cross connection, said U-sh'aped passage being so dimensionedand filled with .water that the period of oscillation of thewater from side to side of the ship, on the occurrence of rolling movements will be substantially equal to the natural period of oscillation of the ship.

5. In ships, means for damping the rolling movements comprising closed water vessels at each side of the Shi and a cross 'connection for the bottom ends of said vessels, said vessels and cross connection forming a U-shaped passage in a vertical plane in which passage the inclosed water may oscil late from side to side of the ship while the lower part of said -U-shaped passage remains filled with water, and means for throttling the passage of air from the upper end of said closed holders comprising, a cross pipe connecting the upper air spaces of said water vessels and a valve for throttling the pas sage of air through said air-pipe.

6. 'In ships, means for damping rolling, comprising water vessels widening toward their upper ends, a cross connection joining the lower ends of said vessels, a cross pipe joining the upper closed ends of said vessels, and means for throttling the passage of air through said last mentioned cross pipe; 7.

n ships, means for damping rolling,

comprising watervessels widening toward their 11 per ends, and arranged one at each side 0 the ship, a cross pipeoining the lower narrow ends of said vessel, and means for throttling the flow of air from the upper closed ends of said vessels.

8. In ships, means for damping rolling,

comprising water (pntaining vessels ar-.

ranged on opposite sides of the ships and widening toward their upper ends, a cross connection joining the lower narrow ends of said vessels, a throttle valve in said connection and. means for throttling the flow of air from the upper closed ends of said water vessels.

9. In ships, means for damping the rollpressure, said U-shaped passage bein so dimensioned and filled with water w ich is free to oscillate, that the period of oscillation of the Water from side to side of the ship, on the occurrence of rolling movements are substantially equal'to thenatural period of oscillation of the ship.

10. In ships, means for damping the rolling movements, caused by the impacts of the waves comprising a water vessel widening toward its upper end at each side of the ship, a cross connection joining the bottoms of said vessels to form a substantially U- shaped passage in a vertical plane, means for maintaining the air above the water levels in both vessels under the same pressure and means for throttling said cross connection, said U-sha d passage being so,dimensioned and fill with water which is free to oscillate that the period of oscillation of the water from side to side of the ship, on the occurrence of rolling movements are substantially equal to the natural period of oscillation of the ship.

11. In a ship utilizingthe oscillation of bodies of water from one side of the ship to the other for damping the rollin the combination of a holder for water 0 substantially U-shape in vertical section, the vertical arms of which are located on either side of the vessel and upwardly gradually increase in horizontal cross-sectional area, means for hermetically sealingthe ends of said arms and means for connecting the upper ends of said arms so as to throttle the flow of air inclosed above the level of the water in one arm to the space above the water in the other arm.

12. In a ship utilizing the oscillation of bodies ofwater from one side of the ship to the other for dam ing the rollin the combination of a hold zar for water '0 substantially U-shape in vertical section, the vertical arms of which are located on either side of the vessel and upwardly gradually increase in horizontal cross-sectional area, means for hermetically sealing the ends of said arms, a pipe connecting the upper ends of said arms and means for varying the rate of flow of air through said pipe.

13. In a ship utilizing the oscillation of bodies of water from one side oi" the ship to the other for damping the rolling, the combination of a holder for water of substantially U-shape in vertical section, the vertical arms of which are located on either side of the vessel and upwardly gradually increase in horizontal cross-sectional area, means for hermetically sealing the ends of said arms, a pipe connecting the upper ends of said arms so as tothrottle the flow of air inclosed above the level of the water in one arm to the space above the water in the other arm and means located at the bottom of said holder for varying the cross sectional area thereof.

14. In a ship utilizing the oscillation of bodies of water from one side of the ship to the other for damping the rolling, the

combination of a holder for water of substantially U-shape in vertical section, the

to the other for damping. the rolling, the

combination of a holder for water of substantially U-shape in vertical section, the vertical arms of which are located on either side of the vessel and upwardly gradually increase in horizontal cross-sectional area, means for hermetically sealin the ends of said arms, and a pipe connectmgthe upper ends of said arms.

. 16. In ships, means for damping the rolling movements, comprising closed water vessels at each side of the shi a cross connection for the bottom ends o said vessels, said vessels and cross connection forming a U- shaped passage in a vertical plane, in which passage the inclosed Water may oscillate from side to side of the ship, the lower part of said U shaped passage remaining always filled with water, and a pipe connecting the aif spaces above the water level in said vesse s. i

17. In ships, means for damping the rolling movements, comprising closed water vessels at each side of the sh1 a cross connection for the bottom ends 0 said vessels, said vessels and cross connection forming a U- shaped passage in a vertical plane, in which passage the inclosed water may oscillate from side to side of the ship, the lower part of said U-shaped passage remaining always filled with water, and a pipe connecting the air spaces above the water level in said vessels, which is adapted to throttle the flow of air from one vessel to the other.

18. In ships, means for damping the rolling movements, comprising closed water vessels at each side of the ship, a cross connection for the bottom ends of said vessels, said vessels and cross connection forming a U-shaped passage in a vertical plane, in which passage the inclosed Water may oscillate from side to side of the ship, the lower part of said U-shaped passage remaining always. filled with water, a pipe connecting the air-spaces above the water level in said vessels and means for varying the cross sectional area of said pipe.

l9. In ships, means for damping the rolling movements, comprising closed water vessels at each side of the ship, a cross connection for the bottom ends of said vessels, said vessels and cross connection forming a U-shaped passage in a vertical plane, in which passage the inclosed water may oscillate from side to side of the ship, the lower part of said U-shaped passage remaining always filled with water, a pipe connecting the air spaces above the water level in said vessels, and means located at the bottom of said U-shaped passage for varying the cross sectional area of said passage.

20. In ships, means for damping the rolling movements, comprisin closed water vessels at each side of the ship, a cross connection for the bottom ends of said vessels, said vessels and cross connection forming a U-shaped passage in a vertical plane, in which passage the inclosed water may oscillate from side to side of the ship, the lower part of said U-s'haped passage remaining the air spaces above the water level in said vessels, means for varying the cross sectional area of said pipe and means located at the bottom of said U-shaped assage for varying the cross sectional area oi said passage.

21. In a ship utilizing the'oscillation of bodies of water from one side of the ship to the other for damping the rolling, the combination of a holderfor water of substantially U-shape in vertical section, the vertical arms of which are located on either side of the vessel, and upwardly gradually increase in horizontal. cross sectional area, means for maintaining the water under equal pressures and means for varying the depth of water in .said arms so that not only may the period of oscillation of the water correspond approximately to the period of oscillation peculiar to the ship, and to the conditions to which it may be subjected, but also so that a difference in phase maybe set up between the oscillations of the water and those of the shlp.

22. a ship utilizing the oscillation of 105 always filled with water, 'a pipe connecting bodies of Water from one side of the ship to the other for damping the rolling, the combination of a holder for Water of substantially U-shape in vertical section, the ver- 5 tical arms of which are located on either side of the vessel and upwardly gradually increase in horizontal cross-sectional area, means locatedat the bottom of said holder for varying the cross sectional area thereof, 10 means for maintaining the water under equal pressures and means for varying the depth of water in said arms, so that not only may the period of oscillation of the water correspond approximately to the period of oscillation peculiar to the ship, and to the 5 conditions to which it may be subjected, but also so that a difference in phase may be setup between the oscillations of the water and those of the ship.

In witness whereof I have hereunto set my 0 hand in the presence of two witnesses.

HERMANN FRAHM. 

